When turbine blades become damaged, they are removed from the turbine rotor for repair or replacement. In some turbines the turbine blades of each circumferential course or row has its distal end secured to a circumferential shroud. The blade has one end, as is well known, attached to the rotor by suitable means such as being configured received in a cooperative opening fashioned on the rotor. To secure the other blade end, each turbine blade has a radially projecting tennon received in a cooperative opening in the shroud. The tennon is mechanically coupled to the shroud as by peening to secure each end of the turbine blade to the shroud.
To remove the damaged turbine blade or blades, the blade end is separated from the shroud as by cutting or other technique which necessarily destroys or damages the tennon. At the rotor, the blade is separated in a fashion commensurate with the manner in which it is attached. Heretofore, depending upon the extent of the repairs necessary, total replacement of the blade may be indicated. The new blade has on one end a tennon thereon to facilitate reconnection to the shroud and the other end fashioned for reconnection to the rotor. New blades are expensive and may be subject to delays in manufacture and shipment. Alternatively, it may be decided to instead repair the blade. During repair it is necessary to reconstruct a suitable tennon on the blade for reconnection to the shroud. One technique, as described in Frasier U.S. Pat. No. 4,896,408 is to provide a new tennon component which is weldably attached to a prepared turbine blade to define the new tennon for re-connection of the blade to the shroud. This technique necessarily requires the construction of a new tennon component, preparation of the end of the turbine blade to cooperatively receive the new tennon component, precisely locating the new tennon component and thereafter securing the new tennon part to the blade end as by brazing or welding. It is submitted that this technique suffers from the deficiencies of being complex and time consuming and subject to problems in regards to locating and maintaining the location during the welding to attach the tennon component to the blade. The new tennon component must be crafted to match a specific blade profile, positioned and secured to define the proper length of the blade for return of the blade to service. Accordingly, a better method and technique are required to reconstruct a turbine blade distal end without suffering from the deficiencies noted above.
It is also known to have the distal ends of the turbine blades of any course fashioned to have an integral shroud. In an integral shroud the distal ends of the turbine blades are cooperatively configured into a shroud component to mate with adjacent blade ends to define a shroud to restrain the movement of the distal blade ends during operation of the turbine. Should the blade become damaged at the distal end, the blade must be removed to be repaired including repairing the configuration of the integral shroud component at the blade distal end. It may also be necessary to completely reconstruct the shroud component at the blade distal end or to fashion one on either a new blade or a blade which heretofore did not have a integral shroud component thereon.
As with shrouded turbine blades, there has been no satisfactory technique to repair and recondition the distal end of integral shroud turbine blades.